Method of distilling liquid mixtures or solutions.



HILIDING OLOF VIDAR BERGSTBM, F STOCKHOLM, SWEDEN.

METHOD OF DISTILLING LIQUIDYMIXTURES OR SOLUTIONS.

Specification of Letters Patent.

Patented July 9, 1918.

Application led January 8, 1917. Serial .No. 141,204.

method of distilling liquid mixtures or solutions for the purpose of driving ofi' volatile substances, said method being principally characterized by the fact that the heat of the vapors generated during the distilling process is utilized for generating steam or vapor from the agent, generally water, which is used for cooling the same. This result is obtained by maintaining between the boiling point of the cooling agent in the cooler or coolers and the temperature of.

condensation of the vapors 1n said cooler or coolers a suiiicient difference for enabling the vapors to generate steam from the cooling agent. This is rendered possible either by performing the distilling Aprocess under such a high pressure that the vapors obtain a temperature which is required for said generating of steam, or by applying a vacuum to the cooling agent, or linally by a combination of both these methods.

Although the invention may be applied to any distilling apparatus in which the vapors developed during the distilling process are cooled by means of a cooling liquid, it is specially suitable to apply the same in connection with column apparatus, principally column apparatus working continuously.

The steam generated from the cooling agent may wholly or partially be used for distillation purposes or other purposes for which steam is used in industrial work, for instance for drying purposes, the object of the invention being to save the costs required for said purposes.

The present invention 1s speqyally adapted for the distillation of highly diluted solutions, for instance methyl and ethyl alcohol solutions such as they are obtained in treating by-products from the manufacturing of cellulose and the like. lt is only by applying the present invention that the distilling off of the alcohol from such diluted, solutions can be rendered economical which is not the case in column apparatus working ysteam for vaporizing in the ordinary manner, this being due to the fact that the consumption of steam in such apparatus has hitherto been too high for making possible an economical recovering of the alcohol contained in such'diluted solutions.

In the following specification a practical form of the present invention is described as applied to a continuous column apparatus adapted for recovering alcohol from a diluted solution by distillation. Such an apparatus which is illustrated on"the accompanying drawing consists, as is well known to those skilled in the art, of the following parts:

l. The vaporizing compartment A where the spirit is vaporized by means of steam and from the lower part of which the solution deprived of spirit is drawn off.

2. The concentration compartment' B where the vapors generated in the Vaporizing compartment and rising from the samev are concentrated and enriched with spirit.

3. The dephlegmator C where the vapors are partly condensed so as to form a return liquid necessary for the concentration.

4. The cooler D in which the vapors distilling oif are condensed.

For vaporizing the volatile substances and for concentrating the same in such a column apparatus considerable quantitiesof steam are generally required. As an example it may be indicated that the consumption of diluted ethyl alcohol solutions and for concentrating the vapors about l5 per cent., and for diluted methylalcohol solutions about 25 per cent. are generally required as calculated on the incoming solution.

lf the solution be introduced into the vaporizing compartment at a temperature which is about the boiling point of the same, the process of vaporizing and concentrating requires just the same quantity of heat (no account being madeV of losses) as that absorbed in the dephlegmator C and in the cooler Don condensing the vapors and cooling dowri` the condensates, that is to say, the. cooling water from the dephlegmator and from the cooler contain the heat required for the va'porizing and concentrating processes.

The said quantity of heat may now, according to my present invention, be obtained in the form of steam if the distillation is executed under such a pressure, that is to say l at such a temperature that the vapors coming from the concentrating*compartment and entering the dephlegmator 4can generate steam from the cooling water in the latter, and, if wanted, also from the cooling water in the cooler. The steam thus obtained corresponds, if the solution is introduced into from the factory maybe used, for instance flue gases, if wanted in combination with preheating of the entering solution by the drawn off solution.

The preheating of the incoming solution i is executed in a special preheater E from which the solution is at nearly its boiling point, introduced into the vaporizing compartment of the column apparatus. Then the distillation of the same takes place under a pressure which makes it possible for the vapors to generate steam from the cooling water as well in the dephlegmator as, if wanted, in the cooler D. The vapors not condensed in the dephlegmator then escape through the conduit :z: into the cooler D where they are condensed.

The pressure in the distillation apparatus may be obtained by means of a valve F or the .like located in the conduit said valve being preferably so arranged that it opens itself only at the desired pressure.

It is evident that, according to the present invention, the valve F or similar device employed for producing a pressure must be located on the outlet side of the cooler inv enerated. In the ex-v which steam is to be ample shown on the rawing it is supposed that steam is to be generated only in the dephlegmator. However, if steam is to be generated also in the cooler D, said valve must be located on the outlet side of the said cooler, e. g. at F. Consequently the above mentioned pressure-` is vto be main' tained not only in the distillation a paratus but also' in the cooler or coolers, rom the cooling agent of'which steam is to be generated.

In the apparatus shown in the drawing the steam is led olf through the conduit y and is introduced into the next column .apparatus in the battery where it acts as heating steam. It may lalso be introduced into the vaporizing compartment of the same is manufactured from the waste lye of sullite cellulose mills) the steam from the cooling water may wholly or partly be utilized for drying the cellulose.

However, steam can, as mentioned above,

be generated from the cooling wat'er not only in the described manner, viz., by maintaining a pressure in the distillin apparatus and in the cooler or coolers, ut also by maintaining a vacuum on the cooling agent. Finally, steam 4mayalso be enerated from the cooling agent by a com ination of the above described methods, z', e. by applyingA a pressure in the distilling apparatus and coolers and a vacuum on the cooling agent.

It is to be noted that a dephlegmator is nothing but a s ecial kind of a cooler and,

conse uentl t e term cooler is in theclaims used as a generic expression for any kind of cooling apparatus where the vapors are cooled and condensed. v i

It is obvious that several lmodifications may be made in the above described practical forms of the process without departing from the scope of the invention, the characteristic feature of which is the utiliz-V ing of the vapors formed .during the distillation process' for generating steam from the cooling agent.

Having thus described my invention, wha I claim. and desire to secure by Patent is:

1. A method of distillin a relatively small amount of alcohol om a larger amount of an aqueous liquid, which comprises boiling the mixture in va column still, while treating the incoming mixture with the vapors pro uced in said boiling operation, and with a heating agent, treating the vapors given ofi' in such boilin operation with condensate produced from ike vapors and dephlegmating the vapors; bringing the so-treated vapors into heat-exchanging relation with a vcondensing cooling fluid, while said cooling fluid is maintained at a pressure sufficiently below the pressure of the vapors, to roduce boiling of said cooling fluid, therey producing steam in commercially useful quantities.

2. 'Ihe method of treating liquid mixtures containing a small percentage of alcohol in a. column apparatus for the purpose of distilling off the alcohol content thereof, which process includes the steps of boiling said liquid. mixture under superatmospheric pressure 1n a column apparatus, maintaining within such column and in the vapor space of the condenser, a pressure above atmospheric, cooling and condensing `said vapors such steam into contact With a further by maintaining an aqueous liquid inheatamount of the alcoholic liquid to be disexchanging relation with said `vapors, while tilled. l v maintaining a pressure onsaid aqueous ln Witness Whereohave hereunto signed 5 liquidwhich is materially below the presmy name.

sure. of the vapors, whereby steam is generated in industrial quantities, and directing LMNG OLOF VIDAR BERGSYTROM. 

